Panoramic position indicator



i 3953 M. WALLACE ET AL 9 PANORAMIC POSITION INDICATOR Filed Dec. 6,1945 8 Sheets-Sheet l :Agwo Fr, i L

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Aprfi 195@ WAL ACE ETAL PANORAMIC POSITION INDICATOR Filed Dec. 6, 1945I 8 Sheets-Sheet 2 395$ M. WALLACE ETAL. 9 9

mmomuc POSITION INDICATOR Filed. Dec. 6 1945 s Sheets-Sheet 4 INVENTOR.M

A EE 25, 1959 Filed Dec. 6, 1945 M. WALLACE ET AL.

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PANORAM-IC POSITION INDICATOR Filed Dec. 6, 1945 s Sheets-Sheet 7 By @/MJ a/w WALLACE EITAL FAN'ORAMIC PGSITION INDICATOR 8 Shaeis-Shes'i; 8

Patented Apr. 25, 1950 PAN ORAMIC POSITION INDICATOR ApplicationDecember 6, 1945, Serial No. 633,138

18 Claims.

- This invention relates to a panoramic-system for indicating theelevation and location of aircraft.

One object of this invention is to provide a simple system forindicating to a pilot the presence and the relative altitudes of othercraft or objects in the space about him, to enable him to avoidcollisions.

Another object of this invention is to provide a single instrument toshow a pilot the elevation of his own craft and the elevations of othercraft or objects in the space about him.

Another object of this invention is to provide a system whereby radiobeacons may be located at and on tramc hazards, such as hills,mountains, buildings, and the like, to give the pilot of an aircraft awarning indication of its presence and elevation, both absolute andrelative to his own.

Another object of this invention is to provide an indiciating systemwhereby a control station located on the ground may have a continuousvisual panoramic indication of the respective elevations of the craftwithin its region of control.

Another object of this invention is to provide a simple system wherebyaircraft and ground stations equipped with the apparatus describedherein may have continuous panoramic indications of the presence and ofthe elevations of each other. Another object of this invention is toprovide a simple method and system of operation for indicating anddisplaying a panoramic view of the relative and absolute elevations of aplurality of aircraft in a predetermined region, on a display surface oneach aircraft and in control ground stations.

Another object of this invention is to provide means for indicating thetraffic at airports and thereby permit expeditious handling of theaircraft from the control station of the port.

Another object of this invention is to provide a simple system forcontinuously indicating the position of a remotely located movablemember.

In air traffic, the ends of speed and of safety can be best achieved ifthe locations of all aircraft are known continuously by operators atground control stations and. by the pilots themselves on the aircraft.The most desirable and most effective knowledge would be that whichcould be derived from a continuously operating display system showingthe instantaneous relative and absolute positions of aircraft in thetraffic zones. 1

As indicated above, an object of this invention is to provide such asystem. In mountainous territory where weather conditions frequentlyobscure the regular guide lights, it would be a positive contribution tosafety if the pilot could have an indication of the height of themountains where he is flying, relative to his own elevation. An objectof this invention is to provide such a system.

In the operation of this system, each aircraft, and where desired, aground station also, is provided with similar equipment. An altimeterwith.

a pointer and a calibrated scale shows the elevation of the carryingcraft or ground station. Associated equipment co-operates with thealtimeter to show the respective elevations of other craft by the samealtimeter instrument. Such associated means comprise a time-measuringdevice to establish a basic time interval of fixed duration that is thesame for all stations, whether on the ground or on an aircraft.

The time-measuring device converts the time interval to a lineardimension that is made equal to the dimension of the altimeter scale. Apoint on the time-interval dimension thus corresponds to a point on thealtimeter scale.

In mechanical form, the time-measuring device may be a clock or areed-controlled directcurrent motor operating at constant speed, or asynchronous motor operating at a constant frequency, fixed for theentire system. The time interval is preferably established as the timeof one rotation of a driven shaft, which may be direct-driven or gearedup or down. An element fixed to the shaft, and rotated thereby, servesas a timing element. In electronic form, the timemeasuring apparatus maybe a cathode ray tube and an oscillator of fixed frequency tocontinuously and repetitively supply a sweep voltage to one set of thedeflecting plates of the tube, through successive time intervals ofconstant fixed duration. In this case the swept cathode ray provides thetime element.

As indicated, each station, on the ground or on an aircraft, is providedwith a device for measuring the elevation of the aircraft or of thestation. Such elevation is then indicated by a suitable element thatassumes a position according to the elevation being measured. An aneroidcell or Bourdon tube may be utilized to position a pointer in a systemof a mechanical type. For an electronic system, the elevation may bemeasured by any suitable electronic-type altimeter and. the measurementindicated by a point function, such as potential or frequency.

'For the purpose ofthis invention, the time then available as a knownmeasuring stick, when properly calibrated. The quantity to be measuredin this case is elevation. The linear dimension to which the timeinterval is converted, is therefore calibrated in units of elevationalmeasure-' ment for the range within which information is desired.

In one form of the invention, to be described herein, the timing deviceon eachaircraft is a syn chronous motor, and the timing element'rotatedthereby is a disc provided with a narrow radialslot and a neon lampbehind the slot to illuminate the slotunder certain conditions,- andthus to cause the slot to function as a pointer. The illu-- mination isby pulse energization of the neon lamp and the action of the disc istherefore stro-' boscopic. The source of the pulse is an altimeter atthe local station or at an external station.

The time required for one rotation of the disc is the basic fixed timeinterval for the system. Since the path of the timing element iscircular, any convenient pointmay be taken as the zero point orbeginning of the time interval as measured on the circular pathof thatpoint. The slot in the disc may be considereda hand or pointer. A scaleis mounted adjacent the disc and is either circular or annular toencompass an entire circle adjacent the path of the slot inthe disc.'The scale thus physically measures one basic time interval in terms ofa circle as a linear dimension, and, in addition, is calibrated for thedesired range of elevational units. For simplicity, the dimension willnow be considered by reference to the central angle of rotation. Theangular movement of the disc through one rotation, or 360 degrees, willbe dimensionally equivalent to the duration of one unit t me interval.

In order to give significance to the position of theelevation-indicating element, the scale is callbrated according to themovement of the elevation-indicating element. The scale in this form ofthe invention is essentially an element of the elevation-indicatingapparatus and is mounted integrally with that apparatus so the entireeleva- 4 ternal craft, in response to the reception of a correspondingsignal.

In one modification of the system, the motordriven disc is provided withonly one slot and one neon lamp to illuminate it, for self-position,indicating pulses as well as for pulses from external craft. A switchoperation by the pilot identifies the self-position-indicating pulse andelevation.

In a second modification, the disc is provided with two slots radiallydisposed, and two neon lamps, each disposed behind one of the slots. Oneneon lamp receives the self-position-indicatlng pulse; the otherreceives the external positron-indicating pulses.

For proper operation of the system, all the synchronous motors shouldhave the proper phase positions relative to the associated calibratedscale of the elevation indicator. Provision is therefore made to permitrelative phase adjustment, between each motor and the calibrated scaleof the associated elevation-indicator, to be made by the pilot at thebeginning of each flight, accordingto a common predeterminedsynchronizing signal available for the system.

In the case of the electronic system, one sweep interval provides thefixed basic or reference timing interval. Those intervals are alsosynchronized and phased at all stations, both on the ground and on allaircraft, so that any positionindicating impulses received on anyaircraft will be properly related to the timing sweep andcorrespondingly positioned on a reference sweep intervalbase line on acathode ray tube, calibrated to a selected range of elevations.

tion-indicating apparatus may be adjustably positioned relative to thesynchronously driven disc.

The calibrated relationship between the scale and itselevation-indicator is not disturbed by such adjustment, but permits thezero point of the scale to be manually positioned for proper phaseposition at a selected point of the disc slot as the zero point of thetime interval. The slot path and the elevation scale range are thus madeco-extensive and properly phased, and the slot at any position in itspath will indicate or read a corresponding elevation on the scale,whenever its associated neon lamp is energized.

As indicated above, the neon lamp is arranged to be energized by avoltage pulse when the associated slot reaches a position adjacent thescale corresponding to the elevation of an external plane. Where severaltiming pulses are received, from several external planes, the neon lampwill be lighted for each of such pulses to illuminate the slot when theslot reaches each position in its path corresponding to the elevation ofan; ex-

Since this sytem providesa local indication of the position of a remotealtimeter indicator, the system obviously may be used to transmitindications ofmovable members generally where they may be related to acalibrated scale or path; and, by extension, the system may be used totransmit instrument readings from or to a remote station.

The general principles and operation of the invention are explained andshown in greater detail in the following description and drawings, in

1 which Figure 1 is a schematic view of an air traffic zone, showingschematically several aircraft between ground and ten thousand feetelevation;

Figure 2 is a schematic View showing the linear equivalence between thedimension of the calibrated scale of the elevation-indicator and theequivalent dimension of a basic or reference sweep time interval.

Figure 3 is a schematic view showing the 1 various elements tobecombined in a mechanical panoramic indicating unit;

Figure 4 is a schematic and block diagram of the equipment at onestation of a system opera ing according to the present invention;

Figure 5 is a schematic view of two units, at separate stations, showingthe relationship between the indicator units'during operation;

, Figure-6 is a schematic and-block diagram similar toFigure 4,but-showing the use of a separate signal lamp to indicate self position;

Figure 7 is a side view of an elevation indicator, partially inelevation, partially in section, and with parts broken away toshow theelements collected into one casing as a unit, to permit mounting on aninstrument panel;

Figure 8 is a front end elevational view of the unit in Figure 7;

Figure 9 is ablock diagram of a circuit at one station of the system,for use with a cathode-ray 75 tube indicator;

Figure illustrates two types of pulses that may be used, one forsynchronizing and the other for position indicating;

Figure 11 is a schematic graph, illustrating the relationship betweenthe linear dimension of the calibrated scale, the equivalent physicallinear dimension of a reference time interval as established for and tobe traversed by a movable element of a timing device, the value and thetime interval of a sweep timing voltage, and the voltage drop across apotentiometer;

Figure 12 is a diagrammatic and block circuit diagram showing the mannerin which the pulsing action is achieved to indicate the position of thepointer of an altimeter;

Figure 13 is a front view of the screen of a cathode ray tube controlledto show a vertical trace;

Figure 14 is a similar view of a cathode ray tube controlled to show acircular trace, with the local pulse and the external pulses on oppositesides of the trace;

Figure 15 is a block diagram showing how a polar tube is energized andcontrolled to permit proper phasing of a circular trace;

Figure 16 is a front elevational view of an instrument showing itspointer in a reading position with respect. to a calibrated scale, withthe pointer being provided with an electromagnet to permit a movingsearch coil to locate the magnet;

Figure 1'7 is a side view showing longitudinally, and in section, theinstrument in Figure 16;

Figure 18 is a schematic and diagrammatic view of a motor-operatedpick-up coil by means of which a pulse may be generated when the coillocates the electromagnet on the pointer of the instrument in Figure 16,so that the pulse may be utilized to transmit intelligence relative tothe position of the pointer.

As shown in Fig. 1, several aircraft may be flying in a traffic zone, orbe otherwise not far apart, at various elevations, as indicated by thedotted lines, A. B, C and D, within a range, for example, of 10,000feet. The spacing shown between the aircraft is for convenience ofillustration and bears no direct relation to the calibrated scale shown.If each pilot could know of the presence of the other craft, and havesome indication of their relative locations, greater safety wouldresult.

In order to provide such information, the present invention utilizes areference time base and establishes a basic operating relationship oflinear equivalence and registration, as shown schematically in Figure 2,between a linear dimension ll, corresponding to the length of anelevationindicating scale calibrated to the elevational range to besupervised (such as 10,000 feet, as for example in Figure 1) and alinear dimension I2, representing the length of a sweep path that istraversed by a timing device in a basic, or reference, time interval.

The manner in which that relationship is established is shown in moredetail in Figure 3, where the various elements are shown, schematically,of an altimeter or elevation-indicator l3 and a sweep timer 14.

The elevation-indicator it may be of any suitable form, and isillustrated here, by way of example, to show certain functionalelements, such as an air-pressure-responsive bellows l5, or anequivalent aneroid cell, mounted on a support l6 and operative through arack and pinion I 1, or its equivalent, to angularly displace a shaft l8and a pointer l9 relative to a calibrated scale 2|, to indicate theequivalent elevation of the altimeter. The scale 2| is also mounted onthe support 16. The pointer l9 carries a small permanent magnet 23 whosefunction is to generate a signal pulse in a pick-up coil connected to anexternal circuit, when the coil is swept past the magnet. The pulse isthus indicative of the position of the pointer [9, as the pick-up coilis periodically rotated past the magnet by an element of the timingdevice Id.

The timing device [4 is shown schematically as consisting of asynchronous motor 25, a drive shaft 26, and a driven element fixed onthe shaft and shown here as a disc 21 provided with a radial slot 28. Onthe disc 21, radially aligned with the slot 28, is the pick-up coil 29referred to, which may be provided with a core 24 to conduct more fluxfrom the magnet 23. Behind the slot 28 a neon lamp 30 is mounted on thedisc to illuminate the slot and cause it to serve as a stroboscopicpointer whenever the neon lamp is flash-lighted by an applied voltagepulse. In a different modification, two slots and two lamps areprovided, as will be explained in Figure 6.

The function of the timing device 14 is to provide the basic orreference time interval that is to serve as the measuring stick for thesystem. That time interval is established as the time of one rotation ofthe disc 21. The disc may be direct-driven by the motor 25, or it may begeared up or down from the motor. The motor is shown as a synchronousmotor, energized from an alternating current source, of a frequency thatis standard for the entire system. The source may be a generator on eachcraft, or the energy may be supplied by modulating a carrier frequencyfrom a ground source and picking off the modulation frequency on theaircraft.

Similarly, any functional equivalent for the synchronous motor might beused to rotate the disc, such as, for example, a clock or adirectcurrent motor, suitably controlled to operate at constant speed.

The operation of the system may now be considered by reference to theelements of Figures 3, 4, 5 and 6.

Assuming the aircraft to be flying at an elevation of 3,500 feet, thealtimeter I 3 will respond and move its pointer is to the dotted-lineposition indicated at Illa, in Figure 3, corresponding to 3,500 feet onthe calibrated scale 2|.

Assuming the synchronous motor 25 to be operating, it is rotating thedisc 21 at a constant speed. The motor disc 21 is co-axially adjacentthe calibrated scale 2| of the elevation-indicator, so one rotation ofthe disc 21 will sweep the calibrated indicator scale 2|. As alreadystated, the angular movement of the disc 21 through one rotation isutilized as a dimensional equivalent of the duration of one referencetime interval. As the disc rotates and moves the pick-up coil 29 pastthe magnet 23 on the altimeter pointer ill, a voltage pulse is generatedin that coil each time the coil reaches a position 29a in alignment withthe elevation-pointer H! at its position 19a.

Thus, a voltage pulse will be generated at each rotation of the disc,always when the coil 29 passes the magnet 23. Each such voltage pulse isutilized to key a transmitter to cause the transmitter to emit a signalpulse, as shown in Figure 4. That signal pulse is received and detectedby a suitable receiver on every other aircraft of the system in thetraflic zone, and at nearby ground stations. The transmission and thereception of the signal pulse may be considered to for the functionaloperation or removing the supri'rnposed or modulating puiseirom itscarrier frequency Wave. -An'y standard receiver m'ay be employed 'forthisiu'ncti'drial operation, The detected pulse is then applied-to -theneon lampa'ifl for ir'nmediate instantaneous 'energization,

The neon lamp 36 is sunported on-o'r with 'the disc "-21 and rotatedtherewith. "Connections to the lampare made through brushes andslipring's 38 on the 'driven shaft or the motor. Sim'ila'rly, brushesand slip ring-s 39 are provided on the motor-shaft for externalconnections to the' pickup coi1 29.

Since all the-motors and discs are-similar, the

operation at a-remote equipmentuponreception of a pulse from thewear-transmitter is the same as the oberation t'ha' t takes placeat thelocal equipmerl t"shown in Figures '3, 4 and 5, upon reception 1 of asimilar signal pulse tram an exterrial trahsm'itter. When that occurs,neon lamp 3!? receivesa s-ignal"energypulse, and flash i-ights andilluminates slot 28 "for -the instant duration of the signal pulsew'hich isbf'the-or'der of time required "for the pick up coil 29 -on theequipment of -the-external craft to mov'e a'few-arigulardegre'es'as itpasses its magnt'23.

Since the sequence of operations from puls'e generation on one craft toflash-lighting-ofthe neon lamp on the receiving-craft "is'substantia'lly instantaneousythe position of the '-'s'lo"t *whendt isflash-lighted on the local or receiving-craft will be practically the"same -'-a's 'the p'ositionof the slot and the'alig'nedjpik-upcoilonthe-external or sending 'craft, "due 5 to the operation of all thesynchrenousmotors in sy'nchronis'm and phase. Sincetheaction'isstrob'oscoliic, the-hashlight ot constitutes a lightedhandol" pointer SllOVllrthe 'corresp'onciin'g position 'at-which thepick -i signal -'pulse is generated "on the sending sitic'in of theelevation 'indi'cator pointer 'j {9 on the sending I or-aft. The slotposition therefore show's' the position-"of the altimeteri'pointeron thesending craft. The pilot Ofthe receiving "craft thus has a continuousin'dication'ofthe ele-"-" vation of the external craft.

Where many cr'aitar'e in the"adjacent"1egion,

each external craft will be sending ia'sigiial. ipulse accordin 'to'itsbosition, and; all I.of .lthose .pulses will be collected andshownispaceddn various positions on the-disc ofthe-eqiupment on ieach ofthe respective receiving craft,-accordingtothe instants of reception.-These; positions-will -con W V ilan'lpdill as "well as: being applied-to l tlieitr'ans-v mitter circuit and. an -antenn'a 40 7 fortransmissionto othervstations.

The location of the local pulse flash on the disc 2? will indicate theself-position of the craft by reference to thetcalibratedscale 2|. Thecircuit for theloc'alj pulse fto atheneonilamp may be controlled byaiswitch :42 and a 'blo'cking condenser t3. The switch :22 may :be-o'fopening or closing typ'eand isoperable by'the pilot to'ascertain whichone of several flashes 'on the disc is the one caused bythelocalipul'se.

Figure 5 s'hows schematically how the system operates between twoequipments, for example, numbered station #1 and station #2 foridentification. The elevation of the Icraftlidentified as station #1 isindicated by #1" pointer H3, at about 2 oclock on itselevation-indicator scale 2l.

At station #2, the elevation of station #2 is'indi catediat aboutio'clock by its pointer 19. V

The elevation of station #1, indicated byfits pointer is at 2oclockpositionis shownat sta-' tion #2 by the illuminated slot in frontof the neon lamp at Z'oclock position. 7

Similarly, the elevation of station #2, indicated by its pointer 1 9,isshownat station #1 by the 4 oclock position of the lneonlamp andslot.

If more craft are in the vicinity of the aircraft at stations #1 and #2,the slotwill be flash-lighted at'the respective'positions for each ofthe other craft, in addition'to-theindicationsalready referred to. 7

While reference'is here made to equipment located on aircraft, it'Willbe clear that the described altimeters or altitude-indicating equipmentmaybe disposed at fixedrstations, or on buildings or mountain tops, ora'tgother pointsiof terrain or construction that might be flyinghazards. "The altitude of each such equipmentrcan needn'otremember'which is his own'pulse indication.

For convenience? and. simplicity. of explanation, it was assumed'thatthe timing motors ;a11 operate -both in :synchronism and phase.

For'proper. operation an assu-ine'drzero point on the disc should'be 'atatspecific point on'its circle of rotation, atthebe'ginningnffa.reference timeinterval th'at is measured byone-rotation of the disc. As already stated, the beginning ofthat'refer'ence time-interval shouldbe'physical'ly in registry withtheiorigin ofvthe calibratedscale Actually, a synchronous motor"starting from rest could achieveisynehronous speed'atannin stant whenits assumed zero pointwould be at'a 'diiierent pointof "its "circle 30frotation. The meters at the variousstations wouldthen operate insynchronismso mr as'speed is c'oncerne'd but 'would not be in -phase.'llndications at a receiving craftiwouldibe outiofzph'asemy:anangle 9corresponding to the out-of-phase angle at the sending craft. That wouldbe the rotational angle between such assumed zero point on the disc andthe point in space at the beginning of the time interval in registrywith the origin of the calibrated scale 2 I.

To correct for such possible phase displacement, the equipment on eachcraft is adjusted at the beginning of each operating flight, byreference to a synchronizing signal pulse that is periodicallytransmitted to all aircraft from a ground station, on a carrierfrequency that is standard for the system. The synchronizing pulse marksthe beginning of each reference time interval, that is of constantduration for the system.

The synchronizing pulse is also arranged to be shown by the disc slot.The radius line of the slot may therefore be appropriately utilized asthe locus of the zero point of the disc, by which the phase adjustmentis to be made.

The phase adjustment is made by the pilot, after starting the motor, byangularly adjusting the motor frame and the altimeter relative to eachother, to register the slot at the beginning of the altimeter scale. Thesynchronizing signal is preferably sent so it will be recognized on thedisc by some characteristic, such as low frequency flicker, todistinguish it from the positionindicating pulses. The motor is thenangularly adjusted to bring the slot position, where lighted by thesynchronizing signal, into alignment with the origin or zero position ofthe calibrated scale. The adjustment may be made by angularly adjustingeither the motor or the altimeter. By way of example, the adjustmentillustrated herein is by angular adjustment of the motor frame. Thatangular adjustment also adjusts the disc angularly since the synchronousoperating relationship between the frame as a stator and the disc aspart of the rotor is fixed, once the motor reaches synchronous operatingspeed and looks into step.

After such phase adjustment, the motor and the altimeter will be inproper phase relation,

with the reference time interval registered with the calibrated scale2|. The position-indicating signal pulses will then have significancewhen read on the calibrated scale 2|.

In the complete indicator as shown in Figure 7, the altimeter isnormally constructed as a unit on its own supporting base or bracket sothat it may be then assembled as a unit without requiring any furtheradjustment of any of its parts. As is shown, the entire unit consists ofone or more aneroid discs 55, which serve to move an arm I? axially, toa position corresponding to the ambient pressure surrounding the discs.Two brackets 50 and 5| are provided to support two bearings 52 in whicha rotatable shaft 53 is disposed to be angularly moved by the arm H. Therotatable shaft 53 supports the electromagnet 23 and serves to positionthe electromagnet 23 in its path at a position corresponding to theelevation. V i

The altimeter unit, as a whole, is disposed in the back section 54 ofthe casing, which is closed at the back by a suitable closure disc 55,after the altimeter unit is properly mounted and secured to the casingsection 55.

The timing motor and its associated elements are disposed in a frontsection 56 of the casing arrangement for angular adjustment of the motor25 is provided by supporting the motor in a bearing mounted on a bracket53 secured to the casing section 56. A gear 68 is secured to the motorframe coaxially with the shaft of the motor. An idler gear 6| engagesthe gear 60, and the idler is engaged by a driving pinion 62 supportedon an adjusting shaft 63. The front end of the adjusting shaft 63 has anadjusting button 65' attached thereto for use by the pilot to rotateshaft 63 and angularly position the motor to bring the lighted slot ofthe disc into proper phase position with the calibrated scale. The idlergear iii is supported on a shaft 86 which is supported between twobearings 6! that in turn are disposed on and supported on the samemounting bracket 58 which supports the bearing 5'! for the motor.

The idler gear 6! is of such dimension as to clear the inside of thecasing section 56 to permit easy assembly of the motor and itssupporting bracket as a unit. Access to the idler gear 6! is providedthrough a slot 68 in the casing section 55 to permit the driving pinion62 to be placed into meshing engagement with the idler Ed.

The front end of the shaft of motor 25 carries the three slip rings 33and the slotted disc 21. The two neon lamps 33 and 39a are also supported at the same end of the motor shaft respectively behind theirassociated slots 28 and 28a. The lamps are connected to the slip rings,as indicated to permit connections to be made to external circuits. Thedisc 21 is surrounded by an annular scale 2! which is calibratedaccording to the range of elevation to be supervised by the instrument.The front end of the casing is enclosed by a glass cover 10 and the twosections of the casing 54 and 55 are arranged to be nested as shown atshoulder H to permit the two sections to be assembled after thealtimeter and the motor have been mounted in their respective sections.The two sections may then be pinned together by screws 12 or otherequivalent means.

As viewed from the front of the instrument only the calibrated scale 2|will be visible when the motor is operating and the lamps are notflashlighted. When either lamp is flash-lighted it will illuminate itsassociated slot 28 or 28a, or if both lamps are lighted the two slotswill appear as lighted lines, radially directed to the value on thecalibrated scale corresponding to the elevation of the equipment fromwhich the signal was received to illuminate either slot at that point.As already explained, the self-position indicating signal willilluminate slot 23a whereas the externally received signals willilluminate the outer slot 28. The synchronizing signal will be receivedat the outer slot 28 and the pilot will recognize it by its flickerappearance. He may then adjust the motor by rotating the adjustingbutton 54 to turn the motor angularly to a position at which theilluminated slot 23 will be aligned with the zero reading on thealtimeter scale 2l. When the disc is adjusted to that position, themotor is in proper phase position and in synchronism with the othermotors of the system, 50' that illumination of the slot there after willhave true position-indicating significan In Figure '9 isshownasimplified block diagram of a similar position or elevation systemoperating and controlled electronically. For identification, thesynchronizing pulses and the position indicating pulses should havedifferent characteristics. Each pulse is superimposed on a highfrequency carrier of different frequency, as indicated in Figure 10. Thesynchronizing pulse may originate'at a ground station of the system, orit may be derived from. a standard time signal fromv an; independentsource. The position-- indicating pulse will be transmitted on anallocated carrier frequency. 7

To'simplify'the description ofthe operation of the system, two separatereception channels" are shown. The synchronizing pulses 81 are receivedon an aerial 85 and fed to a receiver 8! having the usual radio.amplifier and detecting equipment and suitable tuning or' selectedfrequency filtering equipment. Upon detectiom'the synchronizing pulse isfed to a saw-tooth oscillator controlling a sweep circuit 8 5 toinitiate a sweep voltage to be applied to the vertical deflection platesof a cathode ray tube 35 to establish a constant repetitive time base.The-synchronizing pulse thus controls the starting of thesaw-tocthoscillator 85 to establish the starting point of. the reference sweeptime interval of the base line trace between the vertical plates of. thecathode y ray tube 85. The positioning of the trace and the adjustmentof its length may be controlled by the usual adjustments of the tube 3%.

The position-indicating pulse 8d is received through an aerial 582 and areceiver 33 andv after detection and suitable amplification issupplier-l to one horizontal deflection plate of the oscilloscope.

' Since the synchronizing pulse will control the starting point of thereference sweep time intervals on all craft, the sweep actions will allbe synchronized and kept in phase by adjustment of the sweep tracelength to the calibrated base line length at the screen of the cathoderay tube 86. The position-indicating pulse will horizontally deflect theswept vertical trace for the duration of the pulse, at the instant ofreception. The vertical distance of the pulse from the' origin of thetrace will be proportional to the elevation of the equipment from whichthe pulse originated.

The manner in which the local position-indicating pulse 89 is initiatedmay be understood from consideration of the block diagram of Figure 9.The same sweep voltage from the sweep circuit 85 is used to control atrigger circuit 9.! according to the position of the elevationindicator. The'trigger circuit provides a pulse which is amplified by anamplifier 92 and then used to modulate a transmitter 93 connected to asending aerial 94.

The arrangement of the trigger circuit 9| is shown in more detail inFigure 12. The aneroid cell l5 of the elevation-indicator it moves itspointer as a contact arm 95 along a potentiometer 95 that is energizedfrom a voltage source 9'!. The contact arm is connected through a gridresistor 98 to the grid of an amplifier I09, shown 7 for simplicity'as atriode. The grid is also connected through a blocking condenser lfll tothe output terminal of the sweep circuit '85, so the sweep voltage ofcircuit will be periodically and repetitively applied to the gridthrough the condenser.

When the equipmentiis atzero or sea level, the

grid is biased to .cut-ofi by an auxiliaryiresistor voltageimposedbythe. sweep. circuit 85., When the sweep voltage; equals.- the.negative; bias;.the

tube is. at cut-off. An immediate slight; increase in sweep voltage onthe. grid. renders. the.- tube. conductive to drive the trigger circuit9|: to gen-- erate a pulse that is then amplified and. used to. modulatethe transmitter, as shown. inEigu-re 9. The pulse from. the transmitteris thus; transmitted substantially at the instant. the value. or thesweep voltage equals the value of the potentiometer voltage atthe pointof contact of the arm 95. That point in the.- time interval of the sweepvoltage is the same at all stations. This is further shown in theschematic graph of Figure 11. V

Figure 11 shows the relationship between several functions employed inthe system.

The calibrated scale 2! of. the altimeter provides the linear dimensionto which the reference time interval H1 is to be related. The timeinterval is established. over a path. of the.- same dimension as thescale, and to be traversed by a timing; element, such as the path of onerota tion in the case of the motor, or the length of the vertical timingtrace in the case of. the oathode ray tube.

The saw-tooth sweep voltage established by the sweep circuit Figure 9,is represented by the line H2, which is indicated'as being a straightline, although not strictly so. For the purpose of this system theinaccuracy is small enough to be disregarded. The maximum value of thesaw-tooth sweep voltage that maybe generated, or used, determines thevalue of the energizing voltage E H3 that is to be: made availableacross thepotentiometer 96 from the source 91. That source must alsosupply the additional drop across resistor I62 which provides cut-offbias to tube I00.

The contact arm is adjusted by the aneroi'd discs according to altitude.The potential of the contact point above the bottom point P of thepotentiometer is therefore a measure of the altitude, as indicated onscale 2| on a line parallel to the base line of Figure 11.

The duration of the sawtooth sweep voltage H2, or the time required forit to reach its maximum value when starting from zero, may be ad.-justed by varying the constants of the. sweep circuit. Since the maximumvoltage to be generated by the sawtooth sweep voltage is equal to thevoltage which is impressed across the potentiometer 96, the potential atany point corresponding to the contact 95 on the potentiometer t5 willbe equal to a potential to be reached by the sweep voltage at a pointopposite the contact '95 on a line parallel to the base line in Figure11. r i

. Since the reference time interval Ill equals the time required for thesweep voltage H2 to reach its maximum and both are substantially linear,the sweep voltage H2 will have a point of potential corresponding to thepotential at the point of. contact on the potentiometer .96, and thereference time interval will have a corre-- sponding point of timeat apoint where the same parallel intersects the time reference line Ill.

Similarly that point on the time reference calibration IH corresponds toa similar point opposite it on the calibrated scale 21.. Thus the po.--tential at the contact 95 on the potentiometer 96 corresponds to apotential of the sweep Volt- 7 age H2 and to a point on the referencetime interval Ill and to a point representing elevation on the scale 21.

As utilized in Figure 12, the potential at contact 95 is negativerelative to the base point P and the potential of sweep voltage I I 2 ispositive, but for purposes of explanation of Figure 11, the polaritiesmay be disregarded.

As previously explained, when a positive potential impressed on the gridof tube I by the sweep voltage H2 is equal to the negative potentialimpressed on the grid by the contact 95 on the potentiometer 96, thosetwo voltages will neutralize so that the tube bias will be at its cutoffpoint due to the potential across the biasing resistor I02. As the sweepvoltage continues to increase, the bias decreases and the triode I00becomes conductive to energize its load resistor I04 and the triggercircuit I05, and cause a pulse to be transmitted over the aerial 94.

Figure 13 shows the appearance of the cathode tube screen I20 with avertical trace I2I shown representing the sweep voltage II2 of Figure11. The vertical timing trace I2I which serves as the reference timebase, is adjusted by varying the constants of the sweep circuit 85 tothe cathode ray tube, to register the beginning of the trace at theorigin of the calibrated scale adjacent the tube screen. Calibratedscale I22 in this case corresponds to the calibrated scale 2I of therotary type equipment of the first mechanical modification. In order topermit identification of the signals from the external craft, thereceiving signals from external craft are preferably indicated on oneside of the vertical baseline trace I2I, and the self-indication pulseI25 is indicated on the other side of the vertical trace. In order toprovide for the self-indicating pulse I25, a pulse voltage from theamplifier 92 is applied to the horizontal right-hand plate of the tube85, while the pulse voltage is simultaneously applied, through conductorI25, as a blocking bias voltage to the receiver 83.

The pulse voltage from amplifier 92 to tube 86, through conductor I26,has its return ground connection through the left-hand horizontal plateof tube 86 and the output circuit of receiver 83. Thus, the right-handplate 85a of the cathode ray tube 86 is positive when the selfpositionsignal is applied to tube 85, but when external signals are applied,from receiver 83, the left-hand plate 86b is positive. The returncircuit then is through plate 85a, conductor I 29, and output circuit ofamplifier 92 to ground.

For a circular trace, a polar tube is utilized. Self-position isindicated by inner pip I27 and the elevations of external craft by outerpips I28. A calibrated scale I29 is disposed annularly around thedisplay surface of the tube. To obtain the display shown in the Figure14, a circuit as in Figure 15, is used, which is similar to Figure 9except with the addition of elements to provide a circular trace. InFigure 15 the polar tube I30 has its main terminals supplied with avoltage from a phase splitter circuit I! consisting of a resistor I 3Iaand a condenser I BID. The constants of this circuit are made such thatthe voltages applied to the respective pairs of plates will be 90degrees out of phase.

Energy for the tube may be derived from a low frequency voltage, such assixty cycles. This frequency may be generated locally on a craft, orpicked off as a modulation frequency on a carrier from a local station.As shown in Figure 15, such a modulation frequency after beingsegregated by the receiver is passed through the phase changer I32 topermit phase adjustment of the sixty cycle wave to a position where asuperimposed synchronizing pulse on the sixty cycle wave will registerwith the zero position of the circu-- lar trace on the cathode ray tubeI30, at the origin of scale I29. The receiver which receives theposition-indicating pulse is connected to the center electrode I35 ofthe polar tube I30. An incoming position-indicating pulse will thuscause: a radial pip in the circular trace. The angular position of thepip relative to the zero position of the circular trace, when read onthe calibrated scale, will indicate the elevation of the aircraft fromwhich the signal was sent.

In order to insure that the circular trace is in proper phase, a phasechanger I32 is provided to permit the circular trace to be rotatablyshiftedi until the synchronizing pulse I35 on the trace is aligned withthe origin of scale I29. The reference timing interval of the circulartrace is then in registry with the calibrated scale I29. When all of thetubes in the system are thus connected, all corresponding indications onthe several tubes are in synchronism and in phase.

A self-position indicating pulse I 21 is derived from the localassociated altimeter, which may be of the mechanical type shown, or ofany equivalent electronic type which will provide a voltage pulse whoserelation to a reference time base corresponds to the elevation asmeasured.

A sweep circuit I39 is periodically initiated by the synchronizing pulsefrom the phase shifter I32, and caused to impress a saw-tooth sweepvoltage on the grid of tube I00 through condenser IOI, in the mannerexplained in Figure 12. A self-position pulse from trigger circuit 9| asamplified by amplifier 92 is fed to an appropriate stage of theamplifier I40, through a circuit indicated by the dotted lines I4I, toenergize the polar electrode I35 with voltages of polarity opposite tothat of the incoming position pulses, so the self-position pulse I2'Iwill point radially inward from the circular trace for readyidentification.

A directional or sense indication of the source or sources of theexternal elevation-indicating pulses may be obtained by use of acombination loop and sense antenna or double coil antenna.

* The pilot may thus ascertain the relative directional location of apulse-transmitting source or aircraft whose elevation is indicated to bedangerously close to his own elevation. The elative variation of thestrength of the signal pulse will also serve to indicate his approach toor separation from said source.

As shown in Figure 16, the instrument comprises the usual pointer I50,and a calibrated scale I5I. As shown also in Figure 17, the pointer isnormally mounted on a shaft I53 that is operated by suitable mechanismof the instrument, which need not be shown here. The pointer I or theshaft I 53 serves to support one magnet I54 which is to provide themagnet flux to permit a pick-up coil to generate a pulse for signallingpurposes, as previously described.

The front of the instrument is covered by the usual glass cover I55which closes the case to dust, dirt and other foreign materials Theinstrument as shown in Figures lfi'and 17 may embody its normalconstruction and design as adapted for its usual commercial application,and need be modified only to the extent of the addition of the smallmagnet I54. Physical access to the parts within the casing is thereforenot necessary since the magnet I54 on the pointer I59 will provide,inductively, an indication of its position.

The location of the magnet on the instrument may be determined by asuitable search coil,

ascetic H3 ll driven; by; a. mo

whether it is to provide a local; indie non or merely: to provide alcnsflbtame ndi Ifza localindication is. to, be provided, the disc i153.will. be provided: wit-haslot Hi4 and a neon lamp. its for the purposes,already explained. Access to the. coil and; to the neon lamp will bethrough slip-ringv and brush combinations 66? and: lfil; respectiv y,to, permit connections to external circuits, The. pulse generated in thepick-up coil: tea upon rotation, will be, supplied to a pulsing. circuit11 1 9, from which. pulsing energyamplified by amplifier ill will. besupplied toa suitahletransmitter l 12: connected to a transmittingaerial M3, to radiate. a pulse ona care FREE-- ofa high frequency thathas been assigned tothe operation of this system.

The energy from the. transmitting aerial. H3 will be picked up by areceiving aerial 1.15 and suppl-iedto a radio frequency circuit tuned tothe frequency of: transmission of the system, and the pulse thendetected by suitable detecting equipment l'l-I and supplied to a neonlamp l-lli, supported on an arm or disc I19 driven by a synchronousrnotor" $89 that is rotating at the. synchronous driving speed. A slotIll! in the disc H9 will provide a reading on a calibrated scale 1-32that will indicate the position ofthe pointer on the indicatinginstrument in Figure 16, the calibrated scale I82 being calibrated inthe same manner as the scale ISL Energy for. the two synchronous motorswill be supplied from two circuits of the same frequency. for exampleltd and i 55, so that synchronous speed is guaranteed. i hasingadjustment of the two motors Hill and E39 y be made at each end of thesystem in a ma ier already described in connection with the equipment inFigures 7 and 8.

Qur invention thus contemplates the use of a re rence time base as ameasuring medium, nst which other quantifies may be measured The nvnt-ten is n m ed. to of h details oi construction that may beillustrated, since these are merely for illustrative purpo es Vario smodi i ation ma therefore be made of the construction detail and in thearra "'Pflgnt of the circuits without departing it a d s ene 9.? e. intntio as i 11 h p nded claims ims a p iod i base on to said stations andfor generating a n 1 timed with respect to Said periodic time base corn,on to saidstations in accordance with the value of a measurable ntity, afurther stac m is s i a qt s ind ca a ment m e eriodi all e apredetermined sai in svncfireni fm w th llsaid periodic time base, meansfor transi conversi o the quant tie t i e cng said generated signalsfrom each of said or: a pluralityiof-stations, means at in l i for racei-ng said transmitted; signals, and means r a pl ng sis-e ved a a h.laii i o a d d ca or t. ach. at on.-

an at ac o a plurality 3. The combination in accordance. with claim 2and further comprising means. at each station for applying the, signalsgenerated at said station to the indicator-at said station forindicating the time positions o: the last mentioned signals with respectto said recurrent timebase.

e. The combination in accordance with claim 2 wherein. said indicator ateach of said stations comprises a cathode ray tube indicator. meanshaving ray deflecting electrodes and ray modulating electrodes, meansfor periodically deflect:- ing said ray in. synchr'onism withrecurrences of said recur-rent time base ,'and means for modulatingsaidray in response to application of said signals to said indicator.

5. The combination in accordance with claim 2 wherein said indicator ateach of said stations comprises a cathode. ray tube means having raydeflecting means for circularly deflecting said ray in synchronism withrecurrences of said re.- current time base, said cathode ray tube meansfurther comprising means for modulating said ray in response toapplication of said signals to said indicator. 7

6. The combination in accordancewith claim 2 wherein said indicatorscomprise each a mechanically space scanning element synchronized withrecurrences of said recurrent 'time base, said indicators being eachresponsive to signals derived from one of said means for receiving forproviding visual indications at the instantaneous positions of saidspace scanning element which correspond with the times of reception ofsaid signals.

7. The combination in accordance with claim 2 wherein said transmittedsignals are short pulses of radio frequency energy.

8. A method of telemetric communication comprising the steps ofestablishing a common time base at a plurality of stationsQgen'erating apulse at each of said stations having a time position with respect tosaid common'time base determined in accordance with the value of ameasured quantity, establishing a correspondencebetween times along saidtime base and points along a line in space at each of said stations, andindicating the time positions of said pulses by reference to said lineat each of said stations.

9. A method of telemetriccommunication from a plurality of stations to acentral station, comprising the steps of establishing a co'rn'mon timebase said plurality of stations and at said central station; generatingapulse at each of said plurality oi stations; each of said pulses havlng 'a time position with respect to the common time base which isindicative ofthe valubf a rneasurable quantity, establishing a;correspondence between time positions along 'saidcommon timebasejandpoints along aline in space at a cent al station and i isa fiitbs i positions of each generated pulse at sale central it nb jrs en i saime nnat lei qcrsliisat es issas 91'".'.,..b l iss i7 a--similar-periodically recurrent time base ateach of'iaplurality ofstations, means at .each of said plurality: of stations for generatingasignal timed with respect to saidtime base in accordance with the valueof a measurable quantity, an indicator at .each .of said stations. forindicating timing of signals with respect to said-time base, means fortransmitting..said signalsfro mfeach of said stations to the remainderof said stations, and means at each station for receiving signals fromthe remainder of said stations and for applying said signals to theindicator at said each station.

11. In combination, a first cathode ray tube indicator having means forgenerating a cathode ray beam and an indicating surface visuallyresponsive to impact by saidbeamymeans for recurrently and periodically"causing said cathode ray beam to scan-said indicatingsurface; said lastmeans comprisinga source ofsaw-tooth'voltage, means for measuringthe-magnitude of a first physical quantity, means responsive to saidlast means for establishing a direct current voltage proportional tosaid magnitude, means responsive jointly to-said saw-tooth voltage andto said direct currentvoltage' for generating a' first pulse timed inaccordance} with said magnitude, first means for transmitting saidfirstpulse to a remote location a secondcatliode ray tube at saidremotelocationhaving means for generating a cathode ray beam and anindicating surface visually responsive to impact by said cathode raybeam, means for recurrently and periodically causing said second namedcathode ray beam to scan said second named indicating surface, said lastmeans comprising a source of saw-tooth voltage, means for measuring themagnitude of a further physical quantity at said remote location, meansresponsive to said last means for establishing a direct current voltageproportional to said magnitude, means responsive jointly to said lastnamed saw-tooth voltage and to said last named direct current voltagefor generating a further pulse timed in accordance with said magnitudeof a further physical quantity, means for transmitting said furtherpulse from said remote location, means at said first cathode ray tubeindicator responsive to said second pulse for modulating said cathoderay beam of said first cathode ray tube, means at said second locationresponsive to said first mentioned pulse for modulating said secondnamed cathode ray beam, and means for synchronizing said means forrecurrently and periodically causing said cathode ray beams to scan saidindicating surfaces.

12. In combination, a cathode ray tube indicator having an indicatingsurface, a source of saw-tooth voltage, means for estab ishing recurrenttraces on said surface comprising said source of saw-tooth voltage,means for measuring the magnitude of a physical quantity and forestablishing a D. C. voltage having an amplitude proportional to saidmagnitude, pulse generating means responsive to said last mentionedvoltage and to said saw-tooth voltage for generating a pulse at a timeduring said recurrent trace which is representative of said magnitude,means for transmitting said pulse to a remote point, and means at saidremote point for indicating said magnitude, said pulse generating meanscomprising a gaseous conduction device, means for maintaining saidgaseous conduction device o ifbiased in response to said D. C. voltage,and means for appying said saw-tooth voltage to said gaseous conductiondevice as an on-bias volta e.

13. In combination, a cathode ray tube indi- 18 cator-having means forgenerating a cathode ray beam and an indicating sun-ace visuallyresponsive to said cathode ray beam, means i'or recurrentiy andperiodically causing said cathode ray beam 179802411 a circular trace onsaid indicating surface, a saw-tooth voltage generator, means forcontrolling said saw-tooth voltage generator to initiate. generation ofsaw-tooth voltage waves periodically in synchronism with said circulartraces, means for measuring the magnitude of a physical quantity, meansresponsive to said last means for establishing a direct current voltagehaving an amphtudeproportional to said magni tude, means responsivejointlyto said saw-tooth voltage andtosaiddirect current voltage forgenerating a'pulsetimed in accordance with'said magnitude, --and-*-means for transmitting said pulse 14.111 combination, a cathode ray tubeind-icator-having an indicating surface, means for establishingrecurrent traces'on said surface, said means comprising :a saw-toothvoltage generator, means for measuring .the magnitude of a-physicalquantity and for establishing a voltagehaving an amplitude proportionalto said magnitude, pulser means comprising a gaseousuconduction deviceresponsive to said last mentioned voltage and to saidsaw-tooth"voltageforfiring to-generate a pulse at timesduringsaid-recurrent traces representative of said magnitude, means fortransmitting said pulses to a remote point, and means at said remotepoint for indicating said magnitude.

15. In combination, means for establishing corresponding mutuallysynchronized periodically recurrent time bases at each of a plurality ofaircraft, means aboard each of said aircraft for generating a pulsetimed with respect to said time base in accordance with the altitude ofsaid aircraft, an indicator means on each of said aircraft forindicating timing of pulses with respect to said time base, means fortransmitting said pulses from each of said aircraft to the remainder ofsaid aircraft, and means at each of said aircraft for receiving saidpulses from the remainder of said aircraft and for applying said signalsto said indicator at each of said aircraft, visually to indicate therelative altitudes of said plurality of aircraft.

16. In combination, means at each of a plurality of aircraft forgenerating a periodic time base common to said aircraft, and forgenerating at each aircraft a signal timed with respect to said periodictime base common to said aircraft in accordance with the value ofaltitude of said each aircraft, a further station comprising anindicator, said indicator comprising an element moving periodically overa predetermined path in synchronism with repetitions of said periodictime base, means for transmitting said signals from each of saidplurality of aircraft to said further station, means at said station forreceiving said signals and for applying said signals to said indicator,said indicator being arranged to provide a visual indication in responseto each application of one of said signals thereto at the then positionof said moving element.

17. In combination, means for establishing an identical periodicallyrecurrent time base at each of a plurality of aircraft, means at each ofsaid aircraft for generating signals timed with respect to said timebase in accordance with the value of altitude of said aircraft, anindicator at each of said aircraft for indicating the timing of signalsapplied thereto with respect to said time base,

means for transmitting said signals from each of said aircraft to theremainder of said aircraft, means at each of said aircraft for receivingsaid transmitted signals, means for applying signals received at each ofsaid aircraft to said indicator at each of said aircraft, and furthermeans at each of said aircraft for applying signals generated at saidaircraft to the indicator at said aircraft, for indicating timepositions of said last mentioned signals with respect to said recur- 6rent time base.

18. In combination, a cathode ray tube indicator having means forgenerating a cathode ray beam and an indicating surface responsive tosaid cathode ray beam, means for recurrently and periodically causingsaid cathode ray beam to scan said indicating surface, said last meanscomprising a source of saw-tooth voltage, means for measuring themagnitude of a physical quantity, means responsive to said last meansfor establishing a direct current voltage having an amplitudeproportional to said magnitude, pulser means responsive jointly to saidsaw-tooth voltage and to said direct current voltage for generating apulse timed in accordance with said magnitude, and means fortransmitting said pulse, wherein said pulser means comprises a gaseousconduction device having a control electrode, wherein said directcurrent voltage is applied to bias said control electrode, and whereinsaid sawtooth voltage is superposed on said direct current voltage, saidgaseous conduction tube being arranged to fire upon attainment of apredetermined relation between the magnitudes of said direct currentvoltage and said saw-tooth voltage.

MARCEL WALLACE. WILLIAM IEU-LIANG WU.

REFERENCES CITED The following references are of record in the file ofthis patent;

UNITED STATES PATENTS Number Name Date 2,084,760 Beverage June 22, 19372,090,359 Robinson Aug. 17, 1937 2,203,995 Main et a1. June 11, 19402,252,083 Luck Aug. 12, 1941 2,301,929 Budenbom Nov. 1'7, 1942 2,321,605Keinath June 15, 1943 2,321,971 Becker June 15, 1943 2,378,604 WallaceJune 19, 1945 2,400,309 Kock May 14, 1946 2,402,688 Scurnick June 25,1946 2,403,890 Johnson July 9, 1946 2,407,336 Young, Jr. Sept. 10, 19462,415,981 Wolff Feb. 18, 1947 2,421,785 Hathaway June 10, 1947

